The interaction between urbanization and aerosols during a typical winter haze event in Beijing

Abstract

Abstract. Aerosols cause cooling at the surface by reducing shortwave radiation, while urbanization causes warming by altering the surface albedo and releasing anthropogenic heat. The combined effect of the two phenomena needs to be studied in depth. The effects of urbanization and aerosols were investigated during a typical winter haze event. The event, which occurred in Beijing from 15 to 22 December 2016, was studied via the Rapid-Refresh Multiscale Analysis and Prediction System – Short Term (RMAPS-ST) model. The mechanisms of the impacts of aerosols and urbanization were analyzed and quantified. Aerosols reduced urban-related warming during the daytime by 20 % (from 30 % to 50 %) as concentrations of fine particulate matter (PM2.5) increased from 200 to 400 µg m−3. Conversely, aerosols also enhanced urban-related warming at dawn, and the increment was approximately 28 %, which contributed to haze formation. Urbanization reduced the aerosol-related cooling effect by approximately 54 % during the haze event, and the strength of the impact changed little with increasing aerosol content. The impact of aerosols on urban-related warming was more significant than the impact of urbanization on aerosol-related cooling. Aerosols decreased the urban impact on the mixing-layer height by 148 % and on the sensible heat flux by 156 %. Furthermore, aerosols decreased the latent heat flux; however, this reduction decreased by 48.8 % due to urbanization. The impact of urbanization on the transport of pollutants was more important than that of aerosols. The interaction between urbanization and aerosols may enhance the accumulation of pollution and weigh against diffusion.

The regional impact of urban emissions on air quality in Europe: the role of the urban canopy effects

“…The consequences of urbanization (i.e., the transition from rural to urban surfaces) on atmospheric conditions are evident (Folberth et al, 2015), and they affect both the climate (Zhao et al, 2014; Published by Copernicus Publications on behalf of the European Geosciences Union. P. Huszar et al: The regional impact of urban emissions 2017; Huszar et al, 2014;Karlický et al, 2018Karlický et al, , 2020 and air pollution (Freney et al, 2014;Timothy and Lawrence, 2009;Butler and Lawrence, 2009;Im and Kanakidou, 2012;Huszar et al, 2016a), as well as the possible interactions between them (e.g., Huszar et al, 2018bHuszar et al, , 2020aHan et al, 2020;Fan et al, 2020) that often lead to complex counteracting effects (Yu et al, 2020).…”

PM2.5 Influence on Urban Heat Island (UHI) Effect in Beijing and the Possible Mechanisms

“…Yu et al. (2020) analyzed the mechanisms of the impacts of aerosols and urbanization using model, and found that aerosols reduced urban‐related warming during the daytime by 20% as fine particles concentrations increased and also enhanced urban‐related warming at dawn conversely. Li et al.…”

“…Y. showed that aerosol radiation interaction (aerosol-cloud interaction) regulates and reduces the winter UHI intensity in Beijing, with the UHII at the time of daily maximum/minimum temperature exhibiting a decreasing/increasing tendency as PM 2.5 concentration increases. Yu et al (2020) analyzed the mechanisms of the impacts of aerosols and urbanization using model, and found that aerosols reduced urban-related warming during the daytime by 20% as fine particles concentrations increased and also enhanced urban-related warming at dawn conversely. Li et al (2018Li et al ( , 2020 examined potential interactions between urban pollution islands and UHI in Berlin, Germany, and found that urban pollution islands are negatively correlated with atmospheric UHI, but they cause higher surface UHI at night.…”

Vertical Structure of Air Pollutant Transport Flux as Determined by Ground-Based Remote Sensing Observations in Fen-Wei Plain, China

“…Severe haze events caused by particulate matter have occurred regularly in China during recent decades, bringing health hazards and reducing atmospheric visibility [1][2][3][4]. These events have drawn worldwide attention, with many studies reporting frequent severe pollution in China's most developed regions [5,6]. Beside the influence of local emissions and further atmospheric chemical reactions [7], regional transport also plays a key role in pollution episodes [8,9].…”